looks like you shocked it. just keep the normal watering routine and things should get back to normal soon or at least the plant will be fine next year. Why did you amended and do all that? Alkaline Soils? Do you normally do this? I'm not sure if this practice is fine but you should have done this before any blooms were present. The plant is killing off its foliage since it trying to provide nutrients to the blossoms. I have one doing something very similar, although mine was just recently planted and then shock started. The other 7 limes I planted are doing much better than the other one but I am confident it will all work out.

I would cut the blooms off and remove all dead leaves. This should encourage new growth. I did that on a spider mite infested paniculata and within 3 weeks there was all new growth. I also removed all the sickly leaves off a Ruby Slippers oakleaf hydrangea last year when it went into a deep shock. This spring it rewarded me with two large spires of blooms.

Sampson & hcmcdole: I bought it already in bloom. The leaves were yellowing, and I read somewhere on this forum that a weak vinegar solution helps to stop yellowing in gardenia leaves. And with my soil a tad on the alkaline side, I thought it wouldn't hurt. The mixture was 1.5TBSP of vinegar to 1 Gal of water.

Thank you for your input. Sounds like there's still hope for this little guy. I'll remove the blooms and dead leaves and hope for the best.

I am totally new to gardening, and I guess I just made a big blunder as a newbie:(

I would suggest keeping it in bright shade or morning sun (thru 11am to 12pm), well mulched with 3-4" of mulch and water the soil early in the mornings with about 1 gallon of water. Bright shade makes the green blooms last longer. Mine opened in June and are still green.

I am having to water twice a week now that 100 degree temps are de rigueur. I have had some yellowing but just 2-3 leaves only; caused by heat stress probably. Do not fertilize it as they come with those round fertilizer pellets that will last until next year. IN Spring 2015, give it 1/2 to 1 cup of organic compost or cottonseed meal and that should do it for the whole year (liquid fish, liquid seaweed and coffee grounds are ok but stop all ferts in July so it will go dormant in the Fall). Miracle Gro formulations can be high in nitrogen and not slow acting so better go with organic compost (a 1/4 to 1/2 inch layer between the soil and the mulch).

Thanks for the info, Luis. Unfortunately, I left for vacation, and when I came home yesterday, it is completely dead :(
Before I left, I moved it to a bright shaded area and gave it a good soak. I'm hoping it will regrow for me next year :)

Kachana,
In the future, don't add a tablespoon of anything to a gallon of water. It's too strong.
A teaspoon, year, especailly for fertilzier.
And for the future, if you buy any shrub, most of the time, all they need is water and mulch.
Hydra means water.
Especailly hydrangeas.
Sorry this happened, it happens to everyone and then you do better the next year.

Oh! I hope you didn't dig it up. I have had die back to the ground only to have the hydrangea come back full swing in the Spring. These shrubs die horribly, looking like crispy little sticks and huge garden fails. But some of them are amazingly hardy given enough time to reconcile with nature.

Me too. I had a problem with the sprinkler control unit many years ago and ended with a dead looking all brown out hydrangea. Because it happened in the Fall, the shrub went dormant instead and did not leaf out again until the Spring.

I would wait and watch for it to come back out from the base.....these hydrangeas are hard to kill, except when they don't get enough water which can happen easily to a potted plant and may have been the final straw for yours. But what do you have to lose by giving it lots of time to see what happens?

The part above the soil line looks dried out; you can cofirm by pruning the stems in 1" increments until you get to the bottom or until you hit green.

Unfortunately, you cannot tell about the roots by viewing this picture. You can either pull it out to look at the roots or wait and see if it leafs out (keep the soil moist as usual though, including during the winter (but water it maybe once every two weeks or so). Note that when exposed to severe drought, the root ball may repel water and in that case, it is better to water (the first time that is) by pulling the plant out into a pail full of water for around 30 minutes or some time after it stops bubbling. Caution: I had one planted in the ground which waited until Spring to leaf out.